1. Field of the Invention
The invention relates to a solder bath apparatus comprising a vessel for melted solder and a slag stripper which is movable across the surface of the molten solder.
2. Description of the Prior Art
In known solder bath apparatus a heated vessel containing the solder is usually round, in particular of annular construction, and is driven by means of a drive so as to rotate slowly about its axis. The molten solder naturally also rotates with the vessel. In the known apparatus the slag stripper is stationary and extends over the level of the moving melt, the oxide skin formed thereon and referred to hereinbelow as slag skin being continually built up against the slag stripper and being displaced thereby, and by the onfollowing slag skin, beyond the rotating vessel edge into an overflow trough. As seen in the direction of motion of the melt, there is always one place in the known apparatus in which the level of the molten solder is free of slag and this place is therefore suitable for the immersion of objects which are to be soldered.
However, such apparatus suffers from different disadvantages.
To begin with, the vessel containing the molten solder requires a much larger area compared to the area of the place which is suitable for the immersion of the objects. It is a consequence of this substantial area that the vessel must always contain a substantial quantity of molten solder if a useful immersion depth is to be achieved. This also calls for increased heating power so that the molten solder is always maintained at the desired temperature.
Secondly, part of the level of the molten solder in the known apparatus is constantly kept free of the slag skin, i.e. it is quasi-"swept clean" and is therefore exposed directly to the ambient air even if a workpiece is not to be immediately immersed into the solder. This not only accelerates the renewal of the slag skin and therefore a loss of solder material, but at this place also removes from the molten solder the thermal insulating effect which is inherent in the slag skin. As already mentioned, this results in unnecessary loss of solder due to oxidation and heat loss of the molten solder due to convection, such heat loss having to be compensated by an increased heat input into the vessel heating system.
Thirdly, the constant build-up and subsequent displacement of the slag skin into the overflow trough in the known apparatus involves the risk that the displaced slag skin also discharges liquid solder into the overflow trough so that the solder is lost.